Search

BNT-6BT-based lead-free ceramics have gained significant attention due to their relatively large piezoelectric coefficients and tunable morphotropic phase boundary conditions. In this investigation, SrTiO 3 (ST) was added to BNT-6BT ceramics to fabricate the BNT-6BT- x ST (BNBT- x ST) composition. The impact of ST content on the phase structure and dielectric permittivity of the BNBT- x ST ceramics was studied. The XRD refinement data show that with increasing ST content, the crystal structure of BNBT- x ST ceramics was transformed from the morphotropic phase structure (coexisting tetragonal (P4/mmm) and pseudo-cubic (Pmm) phase) to the pseudo-cubic phase. The dielectric permittivity data of the BNBT-80ST showed that the T m (the maximum permittivity temperature) moved to −61.9 °C, which caused the room temperature to fall within the range of T m < T < T B (the Burns temperature). This makes the BNBT-80ST a superparaelectric state in relaxor ferroelectrics (RFE). Furthermore, the maximum energy density and the charge-discharge efficiency of the BNBT-80ST achieved 5.48 J/cm3 and 87% at 495 kV/cm, respectively. The energy density of the BNBT-80ST was improved by 2.97-fold and 49% compared with that of the BNBT-30ST and BNBT-70ST. This is mostly attributed to weakened ferroelectricity and improved paraelectricity in the BNBT-80ST. This investigation demonstrates that BNBT- x ST ceramics can be adjusted to a superparaelectric state with an ST content of 80%. This makes the material to possess both a large polarization and a high breakdown field. This material holds great promise for high energy density capacitor applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel "turn-on" fluorescent chemosensor for the detection of Al3+ was developed. • The probe exhibited anti-interference recognition and low detection limit of 22.0 nM. • The detection mechanism of the probe for Al3+ is the formation of Al-complex. • HL can be utilized as a film to detect Al3+ ions. Many Al3+ sensors have been reported in the literature, the lack of spectral features and poor coordination of Al3+ pose a significant challenge to detection. Herein, the design and synthesis of a Schiff's base (HL) sensor is reported, which exhibits a turn-on response to Al3+ in an aqueous solution, and the fluorescence color of HL from light green to cyan upon the addition of Al3+. The limit of detection (LOD) for Al3+ was determined to be 2.20 x 10−8 M. The mechanism for fluorescence sensing was revealed through the analysis of single-crystal X-ray diffraction, DFT, and UV–vis absorption spectra. HL gradually coordinated with Al3+ during the titration process, leading to the formation of HL-Al crystals. The outcome of this study resulted in the successful preparation and application of flexible and foldable films for visual detection of Al3+. [ABSTRACT FROM AUTHOR]

This study investigated the interfacial bond performances between ordinary Portland cement concrete (OPCC) and self-compacting geopolymer concrete (SCGC). The studied factors include nano-SiO 2 , repair material type, curing time, casting direction, and interface pretreatment method. The interfacial bond performances were assessed by Bi-surface shear and drying shrinkage tests. The evolutions in elemental compositions, hydration products, and microstructure in the matrix and interface were verified by BSE/EDS, XRD, and FTIR tests, respectively. ANOVA analysis was conducted to quantitatively analyze the influences of each factor from a statistical approach. The results demonstrated that the bond strength of SCGC increased by 24.5% to 31.7% compared to conventional OPCC. Meanwhile, geopolymers exhibited more compact microstructures but higher drying shrinkage (ε sh,u =891 µε). While nanofillers significantly amplified the cracking potential of geopolymers, which was attributed to the higher early-stage autogenous shrinkage instead of drying shrinkage. The SCGC showed a high enrichment degree of calcium at the interface, indicating that more calcium-rich products were formed. In contrast, the use of nano-SiO 2 in SCGC caused the enrichment of Na, Al, and Si at the interfacial regions, which provided extra nucleation sites for the polymerization of (C, N)-A-S-H gels. The nano-SiO 2 enhanced the intensity of the hydroxide ion and Si-O-T band and promoted the formation of (C, N)-A-S-H gels. The ANOVA analysis proved that the repair material, nano-SiO 2 , and interface treatment were significant factors to affect the interfacial bond strength. In addition, geopolymer-based repair materials were less sensitive to the casting direction, which differed from the conventional self-compacting OPCC. [Display omitted] • Geopolymer concrete at the same strength grade has 25-30% higher bond strength than conventional OPCC. • Nanofillers amplified the cracking potential of geopolymers due to higher early-stage autogenous shrinkage. • nano-SiO 2 in SCGC caused the enrichment of Na, Al, and Si at the interfacial regions. • geopolymer-based repair materials were less sensitive to the casting direction. [ABSTRACT FROM AUTHOR]